Hi Greg,
The people who designed the drives likely never envisioned the technology would
last more than a few years. 5MB disk drives were replaced by 10MB and 20MB
drives and they went from full-height to half-height. Stepper motor technology
advanced, magnetic coatings advanced, suddenly 40MB and 80MB drives were
possible. Transfer your old stuff off the 20MB drive and dump it... Even today,
1TB drives have 2TB, 3TB and 4TB replacements and even higher capacities.
Ultimately, it's a testament to the original engineers who designed and built
these old drives that with a little bit of dedicated tweaking and cleaning,
this old technology can be resurrected by enthusiasts.
Regards,
Keith
From: 'Gregg Eshelman' via Vintage Macs <[email protected]>
To: "[email protected]" <[email protected]>
Sent: Sunday, 19 February 2017, 1:14
Subject: Re: "Sticky" 80Mb Quantum Drives
Some drives have a rubber or soft plastic bump stop for the head actuator. If
stored for a long period of time with the heads parked, the part of the
actuator that touches the stop can get stuck to it - or the material the stop
is made of can deteriorate and get sticky.
Freezing the drive may harden the stop and if it causes enough differential
shrinkage between the stop and what's stuck to it, it can pop loose.
Some drives use a small magnet to hold the actuator parked, and if left there
for a long time the steel piece on the actuator can become overly magnetized to
where the attraction is too strong for the actuator to overcome to be able to
move.
This also happens a lot in CD and DVD drives left unused without a disc
inserted for a very long time. They use a magnet on one side and a piece of
steel on the other side of the disc clamp. Usually the magnet is on the spindle
motor. Without a disc in, the clamp parts fit closer together and can develop
an attraction too strong for the eject mechanism to separate unless there's a
disc inserted to hold the clamp farther apart.
For that problem in a hard drive, a small piece of aluminum foil flue tape
stuck onto the non-moving side of the stop could keep it far enough apart to
weaken the magnetic attraction. For optical drives I've super glued layers of
thin cardboard onto the clamp hub so that when a disc is in the center of clamp
and hub have a very tiny gap. Without a disc the clamp is kept far enough from
the magnet that it can break the attraction. Even then, some clamps get too
strongly magnetized. (A tape eraser might work to cure this. Take the cover off
the drive and zap the clamp from both sides. I don't have a tape eraser.)
Hard drives and optical drives with the ability to develop this problem
happened because the people who designed them either never envisioned them
being left unused for years, or if they did consider this problem didn't figure
it would/could ever happen. Who would never use a hard drive for a decade or
never put a disk in a drive for years? Making the actuators and eject
mechanisms strong enough to overcome the force of over-magnetized park and disc
clamps would cost more - why bother doing that for a situation that would
'never happen'?
Same thing with hard drives that don't hold the heads in park with a magnet. If
they considered the performance of the bump stop material when something is
pressed against it for years, they likely figured getting sticky was a
non-issue because nobody would ever leave a drive parked and unused for a long
time.
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